Why are my photos (from my private WordPress account) are visible onto Google Image search ?
What can you/I do to delete them all from Google Image ?
I wish to keep my wordpress account PRIVATE and therefore don't want to see all of my pictures onto Google image. Please help

Since your blog was previously public this is an issue of google's cache, not WordPress.

I understand that it can take a month for google to get round to re-indexing your site and removing the cache. You can use google's removal tool to speed it up - but I don't know how quickly that works and you would have caches in bing, yahoo, and other sites too.